The present invention relates to propulsion systems for vehicles or toy vehicles, which have the capability of travelling on the ground or in the air.
It is known to provide a vehicle or aircraft that can travel on land as well as in the air. For example, vertical take-off and landing vehicles or craft such as the Harrier Jump Jet have good capabilities in the air, but are not suited to movement on rough terrain.
It is thus desirable to provide a vehicle having all-terrain capability on the ground as well as vertical take-off and landing and moving take-off and landing air capabilities.
The present invention provides a propulsion system for a vehicle or toy vehicle comprising rotary drive means for driving the vehicle along the ground, the rotary drive means operating in a plane and having a peripheral ground-engagement part, the system further comprising a rotor comprising one or more rotor blades rotatable about a rotor axis for producing thrust, wherein the rotary drive means and the rotor are positioned relative to each other so that during rotation of the rotor, the rotor blades pass through the plane of the rotary drive means, inside the peripheral ground-engagement part.
Advantageously, the propulsion system according to the invention allows travel on the ground by virtue of the rotary drive means and travel in the air by virtue of the rotor.
The invention advantageously provides a compact arrangement by virtue of the rotor blades passing through the plane of the rotary drive means. Further, because the peripheral ground-engagement part extends around the rotor blades to some extent, it protects the blades from contacting external objects. In this regard, it is particularly advantageous if the rotor axis lies in the plane of the rotary drive means, because then the coverage of the blades by the peripheral ground-engagement part is maximized.
The present invention also provides a vehicle or a toy vehicle comprising a chassis and one or more propulsion systems as defined above connected to the chassis.
The invention finds use in many different areas. For example the invention can be used in the following industries:                Toy industry—Radio Control model        Defense industry—use as a spy drone in harsh environments (on land or in air)        Search and Rescue—as a first response vehicle for dangerous environments or natural disasters where many obstacles are present between casualties and rescue team        Film industry—interesting and unique camera perspectives can be achieved with a combination of driving, flying and climbing        Exploration—can get to hard to reach places on Earth or other planets where it may not have been possible to reach before.        
In one embodiment the invention is implemented as a four-wheeled vehicle, ie having four propulsion systems, which can drive as well as fly, is capable of vertical take off and landing, climbing 90° surfaces and driving up side down.
In one embodiment, ground driving can be achieved by a rear wheel drive system, while the front wheels may have only their rotor driven.